Manufacture of aluminum bronze powder



1935- D. M. BOOTHMAN 1, 50

MANUFACTURE OF ALUMINUM BRONZE POWDER Filed March 10, 1932 iv \m J H I I r I,

' igNVENTOR p/p, 162;, 9M

ATTORNEYS Patented Oct. 22, 1935' UNITED STATES PATENT OFF-ICE Dale M. Boothman, Oakmont, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Application March 10, 1932, Serial No. 597,901

5Claims.

"This invention relates to the manufacture of the product commonly known as aluminum bronze powder, that is, aluminum in finely di- 'vided flake-like form, which is useful for many I purposes, especially as a pigment in paint. The invention also relates to the manufacture of shrode, an intermediate product in the production' of aluminum bronze powder.

Shrode, as the term is commonly employed in lo the art, is the product of the first shredding operation in the conventional process which has for years been employed in the production of aluminum bronze powder. It consists of a mass of irregularly shaped, thin, more or less ductile l5 flakes of various sizes (quite large as compared with the particles which constitute aluminum bronze powder) which among other requirements should feel soft to the touch when rubbed be- .tween the thumb and forefinger; It is an inter- I! mediate product, on the character and properties off which depend to a large extent the quality of the powder which is ultimately produced from it. Heretofore in making aluminum bronze powder "the practice has been to reduce thin pieces of aluminum to flake form by successive shredding or stamping operations. This presupposes the manufacturing steps which are required to pro- .duce the thin aluminum. The common method of reducing aluminum to sheet form is, as is well known, the passing of an aluminum ingot or the like through a series of rolls. In making aluminum bronze powder by prior methods this rolling operation is continued until a thickness of metal is obtained which is suitable for shredding or stamping to-shrode, and when such thickness is'reached the' aluminum .sheet is cut up into small pieces of a size which can be con- ...veniently introduced into a stamping mill or shredder. Usually two, but sometimes three,

successive shredding or stamping operations are 'performed subsequently to the rolling of the sheet and cutting it up into small pieces by means of shears. In this country two such operations are performed, in the first of which the hammering is continued until the pieces are so reduced in thickness as to break up into flakes under the action of the hammers, thus produc- .i'ng shrode. The second operation then reduces o the shrode to powder.

Aluminum in sheet form finds a large variety of uses other than in the manufacture of aluminum bronze powder, and it will therefore be understood that the small pieces which are to 5 be fed into the shredders may consist of scrap resulting from the making or fabricating of sheet for other purposes.

In the manufacture of aluminum bronze powder the thickness to which the metal is rolled to fit it for the stamping or hammering is sus- 5- ceptible of some variation but in the past the stamping operation has been started with a metal of a thickness equal to about 0.016 inch.

Some attempt has been made to utilize foil scrap reclaimed from various sources, such as the scrap 3' which results from the trimming of foil inpack form. These attempts, involving further rolling of the scrap and then the usual stampingor shredding, have been only partially successful at best.

In both cases, that is, where the sheet is rolled especially for'making aluminum bronze powder and where the sheet in the form of foil scrap is further rolled, the rolling operation has not been carried beyond or to the point where the sheet 0 with reference to the hammering or shredding operation, the variables which heretofore have received attention are the weight and shape of the hammer, the shape of the anvil, the length v of time of the process, and such other factors as affect the quantity of work done per unit area of metal surface or per unit weight of metal. Prior to my invention it has not been considered feasible to use any other type of reducing means at this stage of the process, the hammering action having been always considered essential to the production of flake-powder .or even of good shrode, notwithstanding the time-consuming nature of the operation,-a period of several hours being required to produce only a few pounds of shrode in a'large stamping machine;

The present invention obviates this and othe disadvantages incident to production methods now in use for the manufacture of aluminum bronze powder. It is an object of the invention to provide a method by which aluminum bronze powder may be produced at lower cost than by rior methods known to me, thereby achieving an dvantageous economy. A further object of the invention is to produce a process which can be practiced with less mechanical equipment than heretofore required to produce a given amount of powder in a given time, with the attendant advantage of reducing the floor space required for such equipment. A further object of the invention is to provide a process requiring less labor to produce a stated quantity of powder. Another object is to provide a process by which foil scrap as well as other material heretofore employed in the production of aluminum bronze powder can be utilized. Still another object is to provide an improved method of producing shrode, and a further object is to provide an efficient apparatus bytwhich the improved process may be carried ou In the course of my efforts to improve the manufacture of aluminum bronze powder I became convinced that the substantial failure of prior attempts to produce powder or shrode by continued rolling was due in part if not entirely to a certain welding together of the pieces of aluminum in passing through the rolls. It appeared that when the thin material broke up, pieces so produced would overlap in a subsequent pass and would be welded together, or caused to adhere in some way, by the pressure of the rolls, thus at-- least partially undoing, so to speak, the previous disintegration. At any rate'I have found' that by preventing such welding or adhesion, the rolling can be carried beyond the point where the metal begins to disintegrate under the action of the rolls, without materially impairing the essential qualities of the powder, and in some cases with improvement in one or another of the desirable properties of the product, such as leaflng power or brilliance. For this purpose 1 coat the thin aluminum with a material which will keep the pieces from sticking togethen'using preferably an organic material of a lubricating nature, for example tallow, lard oil, a fatty acid such as stearic, or a mixture of two or more materials.

The coating may be applied in the course of the. .rolling'operation, preferably when or a little before the disintegration or breaking up of the metal first manifests itself, and the application of the coating may be effected in any convenient manner, as by spraying, or by tumbling the coating material and the pieces of metal sheet or foil in a tumbling barrel or the like, the desire being to distribute the material over the surface in the form of a thin, uniform, film-like layer.

After the metal has been coated it is subjected to further rolling, as by passing it through the same set of rolls a sufilcient number of times or through several sets of rolls in succession, the operation being continued until a powder of satisfactory leaflng power is obtained or until a suitable shrode is produced, in which latter case the material may be reduced to powder in a stamp mill or shredder. I have found, however, that by subjecting the metal to a suihcient number of drawing is merely illustrative of one type Of mill that may be employed.

sary to remove any pieces or particles of metal Referring to the drawingi Fig. 1 is a front eievationof a roll mechanism suitable for carrying out my invention.

Fig. 2 is a side elevation of the mechanism shown in Fig. 1, looking from the right of the s latter figure.

Fig. 3 is a view in elevation, on a larger scale, of a grooved roller of a type which is preferably employed in my invention.

The mill shown in Fig. 1 comprises a base plate I upon which are mounted roll housings 2, 2 carrying a pair of rolls 3, 8. A conventional form of screw-down mechanism 4 is provided to regulate the pressure exerted by the rolls. r

v Fig. 2 shows diagrammatically a conveyor 5 are ranged to feed the material tothe rolls over a chute 6 which may be conveniently secured to the roll housings by brackets 6'. The chute 8, as indicated, is preferably pointed at an angle to the horizontal. A hold-down belt 1|, actuated by any suitable driving mechanism, not shown, 'to' rim at the same speed as the conveyor, may be provided to assist in the feeding of the material. A hold-down belt is particularly desirable in feeding loose foil scrap; which otherwise may have a tendency to pile up in front of the rolls and feed unevenly or not at all. Any suitable scrapers ordoctors, not shown, may be provided if necesthat adhere to the rolls. I have found that in some cases a roll of the general type illustrated in Fig. 3 is of advantage.

For example, in rolhng foil scrap I prefer a roll .which is grooved lengthwise, the grooves assisting in pulling the loose scrap through. In the roll shown in Fig. 3, this purpose is served by the spiral or helical grooves 8. Circumferential grooves I may also be provided in the roll surface. The grooves appear also to facilitate the disintegration of the material after it has been sumciently reduced in thickness, and I prefer to use spirally grooved rolls, so as to avoid a hammering action between the rolls.

It is desirable that the material to be treated, whether in the form of small pieces cut from sheet for the purpose, or in the form of foil scrap, be fed through the'rolis in a thin stream of substantially uniform thickness in which the pieces overlap to a certain extent, as the overlapping arrang'ement of the lubricated pieces assists in breaking up the material into the smaller pieces or flakes which constitute shrode. This is an advantageous feature which greatly decreases the amount of time required to produce good shrode.

It is to be understood that the grooved form of roll is not necessary to the successful practice of my invention. Where it is desired to use this form, both rolls of the set or only one may be grooved, and if more than one set are provided, a one or both of the rolls of the entering set may be grooved and those of the other sets plain.

Power may be applied to one or both of the rolls, as desired. If only one is driven, a slight amount of slippage may occur between the two, a which tends to tear thepieces or flakes and thus facilitates the disintegration or reduction.- The slippage also gives what may be described as a polishing action onj'the shrode or powder, and a like eifect, with better control of the same, can 7| .be obtained by driving both rolls but giving one a higher speed than the other.

I have also found that by the method described satisfactory shrode can beproduced from aluminum sheet 0.016 inch in thickness,. out. into II be successfully rolledinto shrode with as few as two passes.

It is to be understood that the invention is not limited to the specific procedure andapparatus herein illustrated and described but can be carried out in other ways without departure from its spirit.

I claim- 1. In the manufacture of aluminum bronze powder from thin flat aluminum in the form of sheet, foil, and the like, the steps comprising coating the thin flat aluminum with material preventing welding of overlapping pieces under pressure, thinning the coated metal by rolling pressure to break up the metal, and continuing the rolling and consequent thinning to break up the metal into flakes.

2. In the manufacture of aluminum bronze powder from thin fiat aluminum, the steps comprising coating the flat metal with lubricating material preventing welding of overlapping pieces thereof, and by rolling pressure and consequent thinning of such pieces disintegrating the same into flake form.

3. The method of disintegrating pieces. of flat 5 aluminum sheet, foil scrap, and the like, for making aluminum bronze powder, comprising lubricating the flat aluminum pieces, and passing a thin layer of such lubricated pieces in overlapping relation through pressure rolls until by the consequent thinning the pieces are broken up into 4. The method of making aluminum bronze powder from pieces of flat aluminum sheet, foil scrap, and the like, comprising applying a lubricant to the flat aluminum pieces to prevent welding of overlapping pieces under pressure, and repeatedly subjecting such lubricated pieces in overlapping relation to rolling pressure until the same are broken up into powder in the form of flakelike particles.

:5. In the manufacture of aluminum bronze powder, the steps comprising thinning by rolling pressure previously flattened pieces of aluminum coated with material preventing welding of pieces which overlap, and continuing the rolling and consequent thinning of such pieces in overlapping relation to break up the same.

DALE M. BOO'I'HIHAN. 

